The nanofiber electrodes have been considered as promising candidates for commercial proton exchange membrane fuel cells due to their high catalyst utilization and enhanced mass transport efficiency.However,for the fi...The nanofiber electrodes have been considered as promising candidates for commercial proton exchange membrane fuel cells due to their high catalyst utilization and enhanced mass transport efficiency.However,for the first time our research determined that the nanofiber electrodes were restricted by the poor chemical stability of the polymer carriers.To gain further insight into the durability of nanofiber electrodes,both cyclic voltammetry aging tests and Fenton’s tests were conducted.Similar to previous reports,our research demonstrated that nanofiber electrodes showed remarkable stability in the cyclic voltammetry aging process.However,Fenton’s tests indicated that nanofibers in the electrodes would decompose easily while being attacked by reactive oxygen species such as HO·or HOO·,which greatly limits their practicability and reliability.The different performances under the two tests also demonstrated that the cyclic voltammetry aging protocols,which have been applied extensively,cannot well mirror the real operating conditions of fuel cells.展开更多
In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose...In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose challenge to the application of Fe-N-C catalyst.Although considerable work has been done to investigate the degradation mechanisms of Fe-N-C catalyst,most of them are simply focused on the active-site decay,the carbon oxidation,and the demetalation problems.In fact,the 2e−pathway in the ORR process of Fe-N-C catalyst would result in the formation of H2O2,which is proved to be a key degradation source.In this paper,a new insight into the effect of potential on degradation of Fe-N-C catalyst was provided by quantifying the H2O2 intermediate.In this case,stability tests were conducted by the potential-static method in O2 saturated 0.1 mol/L HClO4.During the tests,H2O2 was quantified by rotating ring disk electrode(RRDE).The results show that compared with the loading voltage of 0.4 V,0.8 V,and 1.0 V,the catalysts being kept at 0.6 V exhibit a highest H2O2 yield.It is found that it is the combined effect of electrochemical oxidation and chemical oxidation(by aggressive radicals like H2O2/radicals)that triggered the highest H2O2 release rate,with the latter as the major cause.展开更多
基金National Key Point Research and Invention Program of the Thirteenth(Program Nos.2018YFB0105601 and 2017YFB0102801).
文摘The nanofiber electrodes have been considered as promising candidates for commercial proton exchange membrane fuel cells due to their high catalyst utilization and enhanced mass transport efficiency.However,for the first time our research determined that the nanofiber electrodes were restricted by the poor chemical stability of the polymer carriers.To gain further insight into the durability of nanofiber electrodes,both cyclic voltammetry aging tests and Fenton’s tests were conducted.Similar to previous reports,our research demonstrated that nanofiber electrodes showed remarkable stability in the cyclic voltammetry aging process.However,Fenton’s tests indicated that nanofibers in the electrodes would decompose easily while being attacked by reactive oxygen species such as HO·or HOO·,which greatly limits their practicability and reliability.The different performances under the two tests also demonstrated that the cyclic voltammetry aging protocols,which have been applied extensively,cannot well mirror the real operating conditions of fuel cells.
基金The work was supported by the Thirteenth National Key Point Research and Invention Program(No.2016YFB0101302)。
文摘In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose challenge to the application of Fe-N-C catalyst.Although considerable work has been done to investigate the degradation mechanisms of Fe-N-C catalyst,most of them are simply focused on the active-site decay,the carbon oxidation,and the demetalation problems.In fact,the 2e−pathway in the ORR process of Fe-N-C catalyst would result in the formation of H2O2,which is proved to be a key degradation source.In this paper,a new insight into the effect of potential on degradation of Fe-N-C catalyst was provided by quantifying the H2O2 intermediate.In this case,stability tests were conducted by the potential-static method in O2 saturated 0.1 mol/L HClO4.During the tests,H2O2 was quantified by rotating ring disk electrode(RRDE).The results show that compared with the loading voltage of 0.4 V,0.8 V,and 1.0 V,the catalysts being kept at 0.6 V exhibit a highest H2O2 yield.It is found that it is the combined effect of electrochemical oxidation and chemical oxidation(by aggressive radicals like H2O2/radicals)that triggered the highest H2O2 release rate,with the latter as the major cause.
